free from here

AUX1 means gestures. So if you do the gesture, AUX1 is toggled and that means switching between level and acro for example. Also, gestures are enabled by default.

//#define USE_STOCK_TX

Will enable Trim Buttons for just the buttons. (to use for switching level/acro mode). I think it might be the tx sending a biased center.

The option

#define STOCK_TX_AUTOCENTER

is intended for acro drifting issue, you have to wait 2 seconds on the ground with the sticks centered for this to work. Usually there is enough time after bind.

(with stock H8 Tx only?).

To set it up, in config.h, change to

#define RATES CH_PIT_TRIM

This will put rates switching on the pitch trim button.

change to

#define LEVELMODE CH_RLL_TRIM

This will put level mode/acro mode switching on the roll trim button.

uncomment #define USE_STOCK_TX

Then build target and reflash. Now the quad will start in level mode and high rates whenever you power it up. For low rates press the pitch trim button down, and push it back up for high rates again. For acro mode push the left roll trim button, and pushing it right puts it back to level mode. You can change modes and rates while in the air.